Resistance among tubercle bacilli on the rise

Heidi Syre Carriére.

TB is an infectious disease which affects around 9 million people annually. Out of these, 2 million die – most of them in underdeveloped countries. M. tuberculosis has in latter years developed increase resistance towards the most common anti-TB drugs. Drug resistance is especially prevalent in patients who have previously received anti-TB treatment.

The increased resistance makes it important to map the resistance patterns of M. Tuberculosis in each individual patient to provide optimal treatment. Countries struggling with high prevalence of TB often suffer from limited resources – thus causing the fight against the disease to become even more difficult. “95% of all TB cases, and 98% of all TB-related deaths, occur in underdeveloped parts of the world”, explains Heidi. “The highest prevalence of TB occurs in Asia and in Africa, in areas with limited resources in the health care systems. This means lack of proper equipment, test tubes, and qualified personnel necessary for optimal TB diagnostics.”

Heidi has through her PhD dissertation worked on developing and evaluating a new test, the CONRAS-test, for determining resistance in M. Tuberculosis. The CONRAS-test detects enzyme activity specifically prevalent in M. Tuberculosis in a growth culture supplemented with first-line anti-TB drugs . “The test is based on the activity of nitrate reductase, an enzyme detected in more than 99% of M. Tuberculosis isolates, but which is absent in the more atypical mycobacteria which normally do not cause disease in humans. Enzyme activity will cause a colour change in the growth culture from transparent to pink, and this indicates presence of M. tuberculosis. Colour change from transparent to pink indicates resistance in mediums supplemented with antibiotics”, Heidi explains.

In her dissertation, Heidi concludes that the CONRAS-test is as precise and efficient as reference tests, but also far more reasonable in terms of cost. The test can easily be implemented in laboratories with few resources. Recently, the test was acknowledged by the World Health Organization (WHO) as a new, non-commercial test for detecting resistance.

Heidi hopes that while the world still awaits a better vaccine against tuberculosis, the test can be utilized as a tool for limiting the development of resistance in M. tuberculosis. “This is one of several rapid, low-cost tests for detecting resistance in M. tuberculosis developed recently. It gives countries with limited resources and high prevalence of TB the opportunity to provide each patient with optimal care and treatment.”

Heidi’s public defence will take place on Friday 16th of April at 12.30 pm, Auditorium 1, BB-building. Heidi’s dissertation is entitled: “Antibiotic susceptibility testing of Mycobacterium tuberculosis.”